Ruthenium Vinylidene and Acetylide Complexes. An Advanced Undergraduate Multi-technique Inorganic/Organometallic Chemistry Experiment

This experiment describes the isolation and characterization of complexes containing examples of two important monohapto ligands, namely vinylidene and alkynyl ligands. The former is a tautomer of acetylene that has minimal (10^-10 s) existence as an uncomplexed molecule, providing an interesting example of the stabilization of reactive organic species at transition metals--an important motif in organometallic chemistry. The latter ligand affords complexes that have attracted a great deal of interest recently for their potentially useful electronic or optical properties, illustrating a major focus of contemporary organometallic chemistry, the search for useful materials. The particular strength of this experiment is in demonstrating the utility of a range of spectroscopic and analytical techniques in inorganic complex identification. The students observe unusual chemical shifts in the ¹³C NMR (vinylidene metal-bound carbon), meet heteronuclear NMR (³¹P), assign intense metal-to-ligand charge transfer (MLCT) bands in the UV-visible spectra, observe the utility of mass spectra in characterizing complexes of poly-isotopic transition metals, and are introduced to redox potentials (cyclic voltammetry).